This invention relates in general to a fluid control apparatus and in particular to a control apparatus which uses a helical vane, rotatable about a longitudinal axis of a fluid duct, to direct the fluid out of lateral exhaust ports located on either side of the fluid duct to provide lateral thrust in either direction transverse of the axis of the duct or, by positioning the helix in the neutral position, cause no lateral reaction on the duct.
The invention is particularly useful to provide directional control and stability to a single rotor helicopter. Typically, single rotor helicopters utilize a tail rotor located at the aft end of the tail boom to counteract the torque from the main rotor rotation and to provide directional control moments to the aircraft.
A number of designs have been suggested in which the tail rotor is replaced by fluid jets located in the tail boom of the helicopter.
Such designs are disclosed in U.S. Pat. Nos. 3,486,272, 2,418,697 and 3,957,226, and also in U.S. patent application Ser. No. 07/665,239, filed on Mar. 6, 1991 and assigned to the assignee of this invention.
In these prior art devices, the exhaust fluid is directed from the tail boom duct using movable vanes which swivel about a vertical axis or by axially sliding doors which selectively open exhaust ports on either side of the tail boom. These mechanisms are usually complicated in design and requires substantial actuation force to move the control surfaces into the air stream or have high sliding frictional resistance.
It would, therefore, be desirable to provide a fluid control means which is simple in mechanical design and requires a minimum of power for actuation.